Dr. Pelli works in an area full of mystery. How does our brain turn vision into recognition? How do we recognize our friends? It's a specialty full of debate, with little in the way of generally accepted knowledge.

Most researchers share one assumption: Size has nothing to do with it. When we see the letter "A" two inches high, we interpret it by the same cognitive processes as when we see the letter two feet high.

Dr. Pelli's own work said otherwise. He had just completed research into size and vision when he visited a retrospective of Mr. Close's work in 1987.

As he looked at walls covered with Mr. Close's mosaic-like portraits, the researcher realized his technical and difficult-to-understand research paled in comparison. "I never thought I'd be scooped by an artist," Dr. Pelli said.

Dr. Pelli's newest study, published this week in the leading research journal Science, credits Mr. Close for painting a big, fat X across the assumptions of vision theorists.

The key is in the method of portraiture that Mr. Close has been exploring since the 1960s.

Bob Phillips, curator for 20th-century painting and sculpture for the Toledo museum, said Mr. Close was one of the first artists to use photographs as a kind of visual data. Close's method, at its most basic, is simple enough. Mr. Close segments photographs into grids. He then transfers the grid blocks onto canvas in blocks of color, so that the grid is still apparent in the final portrait.

The museum owns Mr. Close's 1987 portrait of pop artist Alex Katz, but it has been off display while the museum hangs new work in the modern art gallery. Museum personnel hope to reopen the gallery Wednesday.

Mr. Philips said the 8-foot-tall portrait composed of 14,896 three-quarter-inch squares is an example of how Mr. Close has "refined how portraiture was done."

In Dr. Pelli's view, he's also refined an idea for visual scientists.

If a viewer stands near a Close painting, he will see only a collection of squares. As the viewer moves away, the squares abruptly converge into a face. To demonstrate what Dr. Pelli saw as the message in Mr. Close's work, he measured at what distance viewers saw the image of a nose emerge from the work.

Was it simply a matter of the squares blurring into a coherent face at a certain distance? No, says Dr. Pelli. The abrupt transition from seeing a series of blocks to seeing a face was too close to the painting for blurring to have caused it.

So, if our recognition of faces and objects is size-dependent, as Dr. Pelli says and Chuck Close seems to demonstrate, just what is going on?

"This is sort of embarrassing," Dr. Pelli said. "Lots of good people have been working on how we recognize objects, and nobody has a credible theory."

"The one little thing we thought we knew, we don't. So it's embarrassing," he said.

Dr. Pelli said the artist remains mute on the subject of how to view his paintings.

"He's been very steady through his whole career. He's always refrained from telling anyone how to look at" his work, Dr. Pelli said. "He's been very friendly and supportive, but he's refrained from taking a position."

But while Mr. Close's work appears to keep vision scientists in the dark about how we see, it did bring another type of enlightenment to Dr. Pelli.

"I always thought there was a clear line between art and science, and I came out of this being very unsure of that. I started feeling scientists and artists are both trying to understand this natural world. I'd have a hard time saying now that there's anything fundamentally different about us."

BLADE PHOTOS BY DARREL ELLIS [NO LONGER AVAILABLE]
The portrait Alex, above, by Chuck Close is viewed close-up at left. Mr. Close's method, at its most basic, is simple enough: He segments photographs into grids. He then transfers the grid blocks onto canvas in blocks of color, so that the grid is still apparent in the final portrait.